Patent specification No. DE-OS 34 34 653 discloses a parting tool having a knife-shaped blade support which is guided along a dovetail guide in sliding manner in an extended lateral recess of the tool shank. By pressing together the spring-tensioned clamping strips of the tool shank which butt on both sides of the blade support, the blade support in that patent is clamped in the desired position. One drawback of this parting tool is that the minimum dimension of the knife-shaped blade support (determined by the cutting force) must be maintained vertically over the entire length of the blade support because the blade support is braced exclusively by the parallel clamping strips. Accordingly, both clamping strips must be of fixed dimension in order to effect sufficient clamping and bracing of the blade support. This can result in a relatively large parting tool height. The tool of this patent, because of its height and the attendant mounting problems, cannot be used in many machine tools. In addition, the length of the Parallel guide of the knife-shaped blade support in the tool shank of this patent can not be less than a certain dimension in order to assure the adequate bracing of the blade support against the cutting force. As a result, a relatively long tool shank length is a characteristic for this type of parting tool.
Austrian Patent specification No. DE-PS 22 50 332 discloses a parting tool whose blade support has a laterally projecting clamping part guided into a lateral recess of the tool shank along parallel guide surfaces which extend in the direction of the longitudinal axis of the tool. The lower guide surface of the tool shank of that patent verges into a contact surface which is vertically positioned with respect to, and extends to the bottom side of, the tool shank. A segment of the blade support of that patent butts against the contact surface. The segment is elongated in a downward direction at the point it connects to the laterally projecting clamping part. The blade support of the patent is secured to the tool shank by screws and the the blade support does not press directly against the contact surface. The downward elongated section of the blade support of that patent might actually improve the bracing of the blade support, thereby enabling the parallel guide of the blade support to be shortened somewhat. However, because the blade support does not press directly up against the contact surface, tilting of the blade support may occur, such that the blade support-tool shank connection is not sufficiently strong and may produce vibrations and rattling. This limits the use of this type of support. Generally, parting tools of this kind are only useful for "cutting in" operations (rather than "cutting off" operations). The industry sometimes refers to "cutting in" operations as "punching in cutting" or plunge cutting. Typically, such operations are for cutting grooves. A common phrase used by the industry for "cutting off" operations is "parting." The present invention can be used for both cutting in and cutting off operations. U.S. Pat. No. 3 934 320 also discloses a parting tool of this type.
U.S. Pat. No. 2 964 833 discloses a parting tool whose knife-shaped blade support makes contact at the broadside thereof, against a side of the tool shank. The narrow sides of the knife-shaped support are guided by two opposing guide surfaces of the tool shank. The lower guide surface has a flat contact surface which is vertical with respect to the knife-shaped support and the side of the tool shank. A correspondingly shaped countersurface makes contact against this contact surface. The blade support is pressed directly against the flat contact surface by means of slotted flat-head screws. However, even with this kind of parting tool the connection between the knife-shaped blade support and tool shank is not stable for many applications.